Disposable absorbent articles such as disposable diapers are well-known articles of manufacture which are worn by infants and incontinent persons. Disposable diapers are worn about the lower torso of the wearer and are intended to absorb and contain urine and other body exudates thereby preventing these exudates from soiling, wetting, or otherwise contaminating the articles (e.g., clothing, bedding, etc.) which come into contact with the diaper wearer.
When using a disposable diaper, the diaper user fits the diaper on the wearer and fastens it about the wearer's waist by a fastening system to thereby affect a side closure. Fitting the diaper about the wearer usually requires the front and back waist portions of the diaper to overlap each other. Since proper and sustained fit about the waist and legs of the wearer is vital for optimal performance in terms of minimizing leakage of body exudates out of the diaper, a diaper fastening system must be able to provide an effective side closure in which the front and back waist portions are maintained in an overlapping configuration. As the diaper is worn, forces tend to cause the overlapping portions to shift position relative to each other. In other words, the overlapping portions are subjected to forces which tend to cause the portions to assume a position relative to each other which is different from the position they assume when the diaper is initially fitted to the wearer. Unless such shifting is limited, the fit and containment characteristics of the diaper are degraded as the diaper is worn. Thus, the fastening system must be designed to securely engage so it does not separate due to the peel forces and shear stress encountered by the fastening system during use.
As used herein, the term "shear stress" refers to the distributed forces acting tangentially to the surface of contact of the members of the fastening system. During the wearing of a diaper, shear stress tends to cause the members of the fastening system to shift with respect to each other. Shear stress is to be distinguished from "peel forces" which act on the members of the fastening system so as to separate and disengage from each other. A disposable diaper is typically subjected to peel forces in at least three ways. Peel forces are generated by the movements of the wearer during use as they tend to cause the first and second members of the fastening system to pull away from each other, by the wearer in trying to unfasten the fastening system during wear (this being a special problem for disposable diapers worn by infants because infants should not be able to unfasten and remove the diaper on their own), and by the user to check the diaper for soiling or to remove the diaper from the wearer. Because the fastening system should be able to be checked and removed by the user and because the user generated peel forces are much higher than the peel forces generated by the first two methods, the fastening system is preferably designed to have a resistance to peel forces (peel resistance) with respect to only the movement and wearer generated methods. Therefore, the peel resistance should only be great enough to prevent failure of the fastening system during the first two methods but low enough to allow the user to check the diaper for soiling or to remove the diaper from the wearer without undue difficulty or tearing of other members of the diaper.
Therefore, it is desirable to design a fastening system capable of resisting shear stress and peel forces generated by the wearer but having a peel resistance low enough to allow the user to easily remove the diaper or check the diaper for soiling.
Typically, fastening systems have been provided which have adequate shear force resistance to prevent the panels from shifting with respect to each other. However, because the shear forces are so high, the peel resistance of the fastening system is also very high. This is generally the situation because as the coat weight of the adhesive on the smooth surface of the backing web of the fastener is increased to improve the shear force resistance of the fastener, the peel force resistance also rapidly increases. The result is that typical fastening systems may rip the backsheet of the diaper during the process of unfastening it to check if the diaper has been soiled or to adjust its fit, thereby leaving a hole in the backsheet of the diaper and rendering the fastener unrefastenable and the diaper unuseable, due to the high peel resistance of the fastener. Thus, it would be advantageous to provide a fastening system having a high enough shear resistance to prevent the panels from shifting with respect to each other and sufficient peel resistance to prevent failure of the fastening system by the wearer's movements but a peel resistance low enough to allow the user to easily remove the diaper and check for soiling or fit without rendering the fastening system unrefastenable or the diaper unuseable.
It is, therefore, an object of the present invention to provide a unique pressure-sensitive adhesive fastener.
It is also an object of the present invention to provide a pressure-sensitive adhesive fastener having a textured surface.
It is a further object of the present invention to provide a pressure-sensitive adhesive fastener capable of resisting relatively high shear stress while having a desired peel resistance.
It is still a further object of the present invention to provide a fastening system utilizing the pressure-sensitive adhesive fastener of the present invention.
It is an even further object of the present invention to provide a disposable absorbent article such as a diaper having a fastening system that maintains the fit of the diaper at the wearer's waist and legs during wear and that is able to resist peel forces and shear stress encountered during use while allowing the user to easily check the diaper for soiling or to remove the diaper without rendering the fastening system unrefastenable or the diaper unuseable.
These and other objects of the present invention will be more readily apparent when considered in reference to the following description and when taken in connection with the accompanying drawings.